Miscellany

from cmath import *

g = 7
C = [0.99999999999980993, 676.5203681218851, -1259.1392167224028,
     771.32342877765313, -176.61502916214059, 12.507343278686905,
     -0.13857109526572012, 9.9843695780195716e-6, 1.5056327351493116e-7]

def factorial(z):
    z = z + 1
    z = complex(z)
    if z.real < 0.5:
        return pi / (sin(pi*z)*gamma(1-z))
    else:
        z -= 1
        x = C[0]
        for i in range(1, g+2):
            x += C[i]/(z+i)
        t = z + g + 0.5
        c = sqrt(2*pi) * t**(z+0.5) * exp(-t) * x
        i = int(abs(c))
        return i